Setting residual charge at charging stations and destination

Hi, here’s a question to the long-distance professionals. I have been driving only 340km apiece with my EQE500SUV so far. That was elegant, because I could ride through in one slide and at the finish just could charge again of 17% full for the return trip. Now we have to drive a track before 900km. I have seen that you can set the residual capacity of the battery for charging stations and for the destination separately. My question to the professionals: How brave is one when setting for the charging stations? 15% or more? What do you set up for the destination? How sure is it that you can find on the way working charging stations? It is not in the Orient, but only from Nordbaden via Salzburg and Tauernautobahn to Jesolo. What would you like to hire?